Calcium thiocyanate [Ca(SCN)(2)] aqueous solutions above 40 wt % and N-methylmorpholine N-oxide (NMMO) monohydrate, which are known to dissolve cellulose, were found to be good solvents for a polyrotaxane comprising a-cyclodextrin and poly(ethylene glycol). The polyrotaxane could be dissolved up to 12 and 10 wt % in a 40 wt % Ca(SCN)(2) aqueous solution and NMMO, respectively. These are the first instances of a neutral aqueous solution and a cyclic amine oxide, respectively, that readily dissolve the polyrotaxane. These new good solvents, as well as other solvents of the polyrotaxane, except for dimethyl sulfoxide, are identical to those of cellulose, indicating that the dissolution mechanism of the polyrotaxane is dominated by intra- and intermolecular hydrogen bonding of the molecule similar to that of cellulose dissolution. The concentrated polyrotaxane solution in a 40 wt % Ca(SCN)(2) aqueous solution showed apparent thixotropy and spontaneous gelation of the solution caused by a gradual increase in its viscosity. (c) 2007 Wiley Periodicals, Inc.